Disease Progression from Chronic Hepatitis C to Cirrhosis and Hepatocellular Carcinoma is Associated with Increasing DNA Promoter Methylation

Abstract

<b>Background:</b> Changes in DNA methylation patterns are believed to be early events in hepatocarcinogenesis.A better understanding of methylation states and how they correlate with disease progression will aid in findingpotential strategies for early detection of HCC. The aim of our study was to analyze the methylation frequencyof tumor suppressor genes, P14, P15, and P73, and a mismatch repair gene (O6MGMT) in HCV related chronicliver disease and HCC to identify candidate epigenetic biomarkers for HCC prediction. Materials and <br/><b>Methods</b>:516 Egyptian patients with HCV-related liver disease were recruited from Kasr Alaini multidisciplinary HCCclinic from April 2010 to January 2012. Subjects were divided into 4 different clinically defined groups - HCCgroup (n=208), liver cirrhosis group (n=108), chronic hepatitis C group (n=100), and control group (n=100) - toanalyze the methylation status of the target genes in patient plasma using EpiTect Methyl qPCR Array technology.Methylation was considered to be hypermethylated if >10% and/or intermediately methylated if >60%. <br/><b>Results</b>:In our series, a significant difference in the hypermethylation status of all studied genes was noted within thedifferent stages of chronic liver disease and ultimately HCC. Hypermethylation of the P14 gene was detected in100/208 (48.1%), 52/108 (48.1%), 16/100 (16%) and 8/100 (8%) among HCC, liver cirrhosis, chronic hepatitisand control groups, respectively, with a statistically significant difference between the studied groups (p-value0.008). We also detected P15 hypermethylation in 92/208 (44.2%), 36/108 (33.3%), 20/100 (20%) and 4/100 (4%), respectively (p-value 0.006). In addition, hypermethylation of P73 was detected in 136/208 (65.4%), 72/108(66.7%), 32/100 (32%) and 4/100 (4%) (p-value <0.001). Also, we detected O6MGMT hypermethylation in84/208 (40.4%), 60/108 (55.3%), 20/100 (20%) and 4/100 (4%), respectively (p value <0.001. <br/><b>Conclusions</b>: Theepigenetic changes observed in this study indicate that HCC tumors exhibit specific DNA methylation signatureswith potential clinical applications in diagnosis and prognosis. In addition, methylation frequency could be usedto monitor whether a patient with chronic hepatitis C is likely to progress to liver cirrhosis or even HCC. Wecan conclude that methylation processes are not just early events in hepatocarcinogenesis but accumulate withprogression to cancer.